Vehicle steering control apparatus and method

Abstract

A vehicle steering control apparatus has a steering wheel, a steering mechanism mechanically separate from the steering wheel for steering the left and right front wheels and a reaction force motor for imparting an operation reaction force against the steering wheel. A steering motor is provided to impart a turning force to the steering mechanism, while a clutch is provided to mechanically connect and disconnect the steering wheel to and from the steering mechanism. A drive torque detector is provided to detect a drive torque imparted to the steering reaction force actuator. A torque sensor is provided to detect an operating torque imparted to the steering wheel. A clutch connection determiner determines that the clutch is in a connected state when a drive torque direction detected by the drive torque detector and an operating torque direction detected by the operating torque detector are different.

1. A vehicle steering control apparatus comprising:
 a driver operating unit configured to be operated by a driver; 
 a steering unit arranged to be mechanically separated from the driver operating unit and configured to turn at least one steered wheel; 
 a steering reaction force actuator operable to apply an operating reaction force to the driver operating unit; 
 a steering actuator configured to apply a turning force to the steering unit; 
 a clutch operable to mechanically connect and disconnect the driver operating unit and the steering unit to and from each other; 
 an operating torque detector operable to detect an operating torque applied to the driver operating unit; and 
 a controller configured to
 determine a drive torque value based on a drive torque imparted to the steering reaction force actuator, and 
 determine that the clutch is in a connected state when a drive torque direction indicated by the drive torque value and an operating torque direction indicated by an operating torque detection value detected by the operating torque detector are different. 
 
 
   
   
     2. The vehicle steering control apparatus as recited in  claim 1 , wherein
 the controller is further configured to calculate a difference between the drive torque value and the operating torque detection value detected by the operating torque detector, and to determine that the clutch is in a connected state when an absolute value of the difference calculated by the controller is equal to or larger than a threshold value. 
 
   
   
     3. The vehicle steering control apparatus as recited in  claim 2 , wherein
 the controller is further configured to set a first threshold value as the threshold value when the driver operating unit is operated in a direction so as to turn wider or to return toward a non-turning position, and a second threshold value as the threshold value when the driver operating unit is operated such that the operating torque direction is changed, with the second threshold value being larger than the first threshold value. 
 
   
   
     4. The vehicle steering control apparatus as recited in  claim 2  or  3 , wherein
 the controller is further configured to raise a clutch connection diagnostic flag and set a command steering angle to a detected steering angle upon determining that the clutch is in the connected state. 
 
   
   
     5. The vehicle steering control apparatus as recited in  claim 4 , wherein
 the controller is further configured to determine that the clutch is in the connected state and raise a clutch connection confirmation flag when the clutch connection diagnostic flag has been in a raised state continuously for at least a prescribed amount of time. 
 
   
   
     6. The vehicle steering control apparatus recited in  claim 1 , wherein
 the controller is further configured to detect a prescribed condition in which the controller determines if the clutch is in the connected state; and 
 the controller is further configured to execute determination of whether the clutch is in the connected state when the prescribed condition has been detected. 
 
   
   
     7. The vehicle steering control apparatus as recited in  claim 6 , wherein
 the controller is further configured to detect that the prescribed condition exists when an operating speed of the driver operating unit is equal to or larger than a first rate threshold value. 
 
   
   
     8. The vehicle steering control apparatus as recited in  claim 6 , wherein
 the controller is further configured to detect that the prescribed condition exists when a change rate of the drive torque value is equal to or larger than a second rate threshold value. 
 
   
   
     9. The vehicle steering control apparatus as recited in  claim 6 , wherein
 the controller is further configured to detect that the prescribed condition exists when a change rate of the operating torque detection value detected by the operating torque detector is equal to or larger than a third rate threshold value. 
 
   
   
     10. The vehicle steering control apparatus recited in  claim 1 , wherein
 the controller is further configured to exert a torque in an opposite direction of a connection direction of the clutch using the steering actuator or the steering reaction force actuator when the controller detects that the clutch is in the connected state. 
 
   
   
     11. The vehicle steering control apparatus as recited in  claim 10 , wherein
 the controller is further configured to drive the steering actuator using a detected steering angle existing at a point in time when the controller detected the connected state of the clutch as a command steering angle. 
 
   
   
     12. The vehicle steering control apparatus as recited in  claim 10 , wherein
 the controller is further configured to exert a torque in an opposite direction of a connection direction of the clutch using the steering reaction force actuator when a variable gear ratio control is being executed such that a gear ratio becomes equal to or smaller than a clutch connection gear ratio at a point in time when the controller detected the connected state of the clutch. 
 
   
   
     13. The vehicle steering control apparatus recited in  claim 10 , wherein
 the controller is further configured to determine that the clutch has been disconnected when the absolute value of the difference between the drive torque value and the operating torque detection value detected by the operating torque detector is equal to or below a third threshold value and the direction of the drive torque value and the operating torque direction of the operating torque detection value detected by the operating torque detector are equal. 
 
   
   
     14. A vehicle steering control method comprising:
 providing a driver operating unit configured to be operated by a driver to input an operating torque to a steering unit that is configured to turn at least one steered wheel, with a steering actuator configured to apply a turning force to the steering unit based on the operating torque and a clutch selectively operable to mechanically connect and disconnect the driver operating unit and the steering unit to and from each other to selectively transmit the operating torque to the steering unit; 
 providing a steering reaction force actuator operable to apply an operating reaction force to the driver operating unit; 
 detecting a direction of a drive torque imparted to the steering reaction force actuator coupled to a driver operating unit; 
 detecting an operating torque direction of the operating torque applied by the driver to the driver operating unit; and 
 determining that the clutch is in a connected state when the direction of the drive torque imparted to the steering reaction force actuator and the operating torque direction of the operating torque are different.